Southern California -- this just in

An estimated 2,500 unionized nurses employed by health provider Kaiser Permanente began a three-day strike Wednesday morning to protest, among other things, increases in their own health insurance costs.

Strikers said their numbers would swell Thursday to include another 19,000 Kaiser healthcare workers statewide, affecting all of the close to 300 Kaiser sites in California.

An organizer called it the largest strike in the history of the Oakland-based healthcare provider. Kaiser has 6.5 million health plan members in California.

[Updated at 12:16 p.m.: In a statement, Kaiser Permanente called the strike "very disappointing and counterproductive."

Company officials said they would continue to bargain in good faith with the union. Its contract proposals "will ensure Kaiser Permanente will remain a great place to work for NUHW-represented employees, and that they will continue to receive highly desirable, market-competitive compensation and benefits."

Kaiser medical centers and offices would remain open through the strike, according to the statement.]

In Los Angeles, most of the strikers planned to picket Wednesday until early afternoon outside Kaiser Los Angeles Medical Center at Sunset Boulevard and Vermont Avenue in Hollywood.

Others were protesting at Kaiser sites in Fontana and San Diego. A representative for Kaiser was not immediately available early Wednesday.

In negotiations dating to May 2010, Kaiser has been asking Southern California nurses to pay more for their health insurance and pay a higher co-payment for each visit to a doctor, said John Borsos, vice president of the National Union of Healthcare Workers, based in Emeryville, which represents 4,000 Kaiser employees.

Nurses also were protesting the lack of voice they have in staffing levels, and the elimination of their pension plan that Kaiser is proposing, Borsos said.

“This is at the same time that you have [Kaiser] executives with eight pension plans" to choose from, Borsos said, “and they’re trying to eliminate the one plan that caregivers have.”

Kaiser, Borsos said, “has made $5.7 billion in profits since 2009. Even though they’re supposed to be not-for-profit, you see enormous profits generated.”